In current cellular mobile broadband systems the achievable data rates are strongly dependent on the users' positions in the network.
In order for wireless networks operators to solve one of their biggest problems—how to get more signal strength where one needs or wants it most, the operators have started in the recent years to deploy their own or rely on end users to buy very small Base Stations, in order to meet the increasing demand for data traffic. This new type of cell sites, referred to hereinbelow as “small cells” or “metro cells”, used in conjunction with wireless cells of the traditional cellular networks (macro cells). Networks that include both macro cells and metrocells are referred to herein as heterogeneous networks (HetNets).
The term “small cells” as used herein and throughout the specification and claims encompass femtocells, picocells microcells and metrocells. Small-cell networks can also be realized by means of distributed radio technology consisting of centralized baseband units and remote radio heads. Beamforming technology (focusing a radio signal on a very specific area) can be utilized to further enhance or focus small cell coverage. A common factor in all these approaches to small cells is that they are centrally managed by mobile network operators.
Small cells provide a small radio footprint, which can range from 10 meters within urban and in-building locations to 2 km for a rural location.
According to the solution being adopted by the operators, the end-users may buy small devices that are personal cellular base stations. The device typically has an antenna to boost the available signal as well as an Internet connection. The device uses the end user Internet connection to connect to the service provider's network and to route the user's phone calls.
With small cells deployed in a single carrier shared with the macro cells in the network, UEs at (or near) the coverage area of a small cell could ideally camp on it to offload the macro network. However, since the power disparity between the macro cells and the small cells is very large, normal cell selection/re-selection procedures will typically result in UEs camping on the macro network for which power levels are higher, even though much larger capacity can be provided by the small cells layer.